| MAX Routledge Services Ltd | Godalming | 2016 |
| Maxey Lawn Care Limited | Spalding | 2017 |
| Maxfarms Ltd | County Tyrone | 2000 |
| Maxi Light Brand Management (UK) Co., Ltd. | Beckenham | 2025 |
| Maxi Sustainable Agriculture Limited | Leicester | 2021 |
| Maxmart Impex Ltd | Coventry | 2015 |
| Maxtrak Limited | Nr Kendal | 2005 |
| Maxwell (NI) Limited | Dungannon | 2013 |
| Maxwell Brothers Limited | Annan | 2008 |
| Maxwell Farms Limited | Turriff | 1995 |
| Maxwell Fisheries Limited | Strangford | 2014 |
| Maxwell Poultry Ltd | Preston | 2013 |
| Max’S Meat Limited | Abingdon | 2026 |
| MAY (Priorton) Limited | Wellington | 1960 |
| MAY Blossom Farm CIC | Rugby | 2022 |
| MAY Brothers Limited | Barnstaple | 1958 |
| MAY Hill Woodlands Ltd | Longhope | 2018 |
| MAY Pigeons Limited | St. Albans | 2025 |
| MAY Pigeons Racing & Breeding Centre Limited | St. Albans | 2021 |
| MAY XYZ Limited | Bedford | 2018 |
| Maya Mushrooms Ltd | Cheltenham | 2018 |
| Maydale Falcons Ltd | Glasgow | 2017 |
| Maydays Farms Ltd | Colchester | 2020 |
| Maydene Ltd | Colchester | 2017 |
| Mayfair Bloodstock Limited | Towcester | 2017 |
| Mayfair Polo Limited | Nottingham | 1996 |
| Mayfield Alpacas Farm and Animal Sanctuary Limited | Sheffield | 2024 |
| Mayfield Animals Limited | Liskeard | 2026 |
| Mayfield Forestry Ltd | Droitwich | 2022 |
| Mayfield Honey Ltd | Kidderminster | 2021 |
| Mayfield Lavender Limited | Epsom | 2006 |
| Mayfield Livery Ltd | Norwich | 2023 |
| Mayfield Nursery (York) Ltd | York | 2012 |
| Mayfield Sussex Beef Producers Limited | Croydon | 2000 |
| Mayfieldholidays Ltd | Gloucester | 2024 |
| Maylands Farm Limited | Trowbridge | 2025 |
| Maynards Sanctuary Ltd | Tunbridge Wells | 2022 |
| Mayo Farm Systems Ltd | Cardiff | 2026 |
| Maypole Equestrian Centre Limited | Wigan | 2004 |
| Maypole Farm Limited | Dromore | 2010 |
| Mayroyd Limited | North Yorkshire | 2002 |
| Mays Farm Limited | Polegate | 1995 |
| Maythorne Trees & Woodlands Limited | Glastonbury | 2025 |
| Maywood Stud Ltd | Salisbury | 2026 |
| Mazdehee Tea Company,Limited(The) | Near Sevenoaks | 1890 |
| Mazotta Limited | Cowbridge | 2020 |
| Mazra Farm Ltd | Dunmow | 2025 |
| Mazubi Orchids Ltd. | Bognor Regis | 2025 |
| MB Aquaculture Limited | London | 2017 |
| MB Bobena Limited | Fraserburgh | 2005 |
| MB Daystar BF. 250 Limited | Fraserburgh | 1989 |
| MB Elliott Limited | Enniskillen | 2017 |
| MB Farming Limited | Bungay | 2018 |
| MB GH Limited | London | 2018 |
| MB3 Estates Limited | Peterhead | 2018 |
| MBC (Estates) Limited | Oxford | 1995 |
| MBC Agri Services Limited | Dumfries | 2025 |
| MBC Bird & Pest Solutions Limited | Dorchester | 2013 |
| MBD Services (Staffs) Ltd | Uttoxeter | 2023 |
| Mbeq Consulting Limited | Dalry | 1998 |
| MBM Enterprises Devon Limited | Tiverton | 2018 |
| MBP Fishing (Scotland) Ltd | Avoch | 2025 |
| MBR Acres Limited | Hull | 2017 |
| Mbsankey Ltd | Wolverhampton | 2025 |
| MBT Engineering and Fabrication Ltd | Wick | 2012 |
| MC & LM Pincombe Limited | Umberleigh | 2006 |
| MC Blades & SON Ltd | Market Rasen | 2013 |
| MC Ginn Farming Enterprises Ltd | Newry | 2015 |
| MC Kittyz Ltd | Littlehampton | 2022 |
| MC Marshall Farms Limited | York | 2020 |
| MC Steading Ltd | Burntisland | 2019 |
| MC2 Consulting Ltd | Bishops Castle | 2003 |
| MC2 London Ltd | Lincoln | 1998 |
| Mcaleer Farms Ltd | Omagh | 2014 |
| Mcallister Enterprises Limited | Fraserburgh | 2002 |
| Mcallister Marine Services Limited | Newton Stewart | 2001 |
| Mcardle Farm Produce Ltd | Armagh | 2022 |
| Mcardle Fresh Produce Ltd | Armagh | 2024 |
| Mcardle Mushrooms Ltd | Armagh | 2020 |
| Mcashwey Stud Limited | Lutterworth | 2017 |
| Mcauley Limited | Bury St Edmunds | 2016 |
| MCB Tree Management Ltd | Bristol | 2023 |
| Mcbride Marine Services Ltd | Kilkeel | 2022 |
| Mcbride Pigs Limited | Omagh | 2014 |
| Mcbride Seafood Ltd | Lurgan | 2018 |
| MCC Farmland Ltd | Londonderry | 2021 |
| Mccain Farms of the Future G.B. Limited | Scarborough | 2025 |
| Mccain Foods (G.B.) Limited | Scarborough | 1962 |
| Mccallum Shellfish Limited | Tarbert | 2006 |
| Mccann Agri Ltd | Newry | 2026 |
| Mccardell and Thompson Ltd | Newquay | 2018 |
| Mccarroll and SON Limited | Ballymena | 2015 |
| Mccarthys (Wickham) Limited | Fareham | 2011 |
| Mccartney Sport Horses Ltd | Stratford-Upon-Avon | 2021 |
| Mccaskie Lime Ltd | Omagh | 2012 |
| Mcclay Engineering Limited | Dereham | 2016 |
| Mccloskey Farms (Cool) Ltd | Claudy | 2020 |
| Mccloskey Farms Ltd | Ballymoney | 2012 |
| Mccloskey Livestock Ltd | Dungiven | 2014 |
| Mccollum (Drumcroon) Limited | Co Londonderry | 1962 |